Booster Tune Monitor

General Description:

The booster tune monitor is a diagnostic used to measure the vertical and horizontal transverse resonant frequencies (or betatron tunes) of the beam accelerated in the booster. The beam is accelerated from 200MeV to 6GeV in 50ms. During this acceleration cycle, the tunes are not perfectly constant and it can be nescessary to precisely measure them along the cycle, in less than 1ms for each tune sample. To measure the tune we must excite a beam position oscillation using a magnetic shaker, record the beam position oscillation using beam position monitorrs (BPM) and perform a frequency analysis of these signals. The layout of this diagnostic is shown on the figure 1.

Figure 1: Layout of the SY Booster tune monitor

This equipment main components are :

-         A DSP board for the processing of the beam position signals to calculate the tune using a 1024 points FFT.

-         A high voltage pulser to drive the beam shaker with 100A-1ms current pulses and perform a single turn excitation of the beam.

-         A 700W noise source to drive the beam shaker to perform a multiturn beam excitation over the full acceleration cycle. 

-         A Labview based application integrating the control of all the parameters of the system and a convenient display of the tune measurements.

The front panel of the Labview application is shown on figure 2.  This application allows now an automatic acquisition of the tunes all along the acceleration cycle, making the routine check of the booster optical setting or the booster machine studies much easier: The system configuration is done in a graphic window. The automatic measurement of all the tunes along a cycle can be programmed: then, all along the measurement cycle the application displays each spectrum in order to check that the FFT processes valid beam signals resulting in a single clean main tune line. After each FFT computation, the frequency of the peak line of each spectrum is recorded and added to the left plots (blue and red plots on the left of the window.

Figure 2: control panel of the SY tune monitor developed using LabView.

Tunes detection results

Record of the tunes during the ramping:

Ibeam= 5mA ,   shaker in single shot,  strength= 3.6, averaging= 3,  acquisition rate= 1sec.